Generally, interest in hybrid vehicles has increased due to a demand for improving fuel efficiency and due to the need to comply with enhanced regulations for vehicle exhaust gases.
In particular, a transmission-mounted electric device (TMED) type hybrid vehicle includes at least one motor and one engine. The vehicle may further include: a battery stored with high voltage electricity for driving the motor; an inverter for converting a DC voltage to an AC voltage; and a clutch arranged between the engine and the motor to transmit the power of the engine to a drive shaft.
The TIED type hybrid vehicle engages or releases an engine clutch during driving in a hybrid electric vehicle (HEV) mode or an electric vehicle (EV) mode according to acceleration/deceleration, a load, vehicle speed, a state of charge (SOC) of the battery, etc., all of which are determined through an operation of an accelerator pedal and a brake pedal that both may be manipulated by a driver.
For example, if a situation in which the battery charge is limited occurs while a hybrid vehicle is driven in the EV mode, an engine clutch may be engaged to perform the HEV drive mode in which the engine power is used.
In order to engage and maintain the engaged state of the engine clutch, the engine should remain at an idle revolution per minute (rpm) speed. However, when the vehicle is driven in a highly-loaded condition such as uphill driving and is driven at a low speed, it is impossible to maintain the engine at the idle rpm. Herein, a transmission clutch may be controlled to slip, thereby maintaining a lock-up state of the engine rpm and the engine clutch.
However, when the slip occurs consistently on the transmission clutch due to continuous driving in a highly-loaded condition, the transmission clutch may be damaged by heat caused by the slip.
In the related art, to prevent thermal damage to the transmission clutch, the transmission clutch may be disengaged. However, there is a problem that the driver cannot drive the vehicle, and therefore, a vehicle travelling performance is degraded when the clutch disengages.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.